Lawyers are asking London’s Court of Appeal to set a minimum term sentence instead.

They also want to reduce the 30-year minimum imposed on Kiaran Stapleton – the 21-year-old self-styled ‘Psycho’ who executed Indian student Anuj Bidve in Manchester.

David Perry QC, for the Crown, said a whole-life order is reserved for ‘rare cases of exceptional gravity’ but conceded the order for Roberts was ‘wrong in principle’.

Lord Justice Leveson claimed the issue was not about ‘letting people go’ and that if an offender was not safe to release they should stay in prison for ‘as long as it takes and if that is forever then so be it’.